The objectives of the continued studies of cell membranes outlined in this proposal are to define the role of the membrane in the survival and function of blood cells. In particular, studies of changes in membrane lipid and protein metabolism which influence cell flexibility and permeability are proposed. Four major areas of interest are underway as follows: 1) Biochemical and biophysical studies to explore the organization of red cell membrane lipid and protein; 2) Biochemical studies to explore the role of membrane kinase and ATP in the regulation of red cell shape and deformability in both normal and pathologic red cells; 3) Studies with a "hybrid" membrane-hemoglobin model to explore the possible role of hemoglobin interactions with the membrane in influencing its function; 4) Studies on the influence of membrane lipid peroxidation on biochemical and physical characteristics of membranes and the possible role of cellular hemoglobin in modulating these reactions. Conventional methods include lipid analyses (TLC and GLC), protein analysis by polyacrylamide gel electrophoresis and enzyme analyses. Additional methods employed will include the active and passive labeling of membrane constituents followed by exchange studies of inside-out and rightside-out membrane vesicles with plasma; a novel method for resealing membrane ghosts around exogenous hemoglobin; red cell membrane fusion with lipid liposomes to modify lipid environments; measurement of the effects of protein kinase and peroxidation in red cell membranes by physical methods including nuclear magnetic resonance, electron spin resonance, and optical rotatory dispersion; and doubly labeled in vivo cell survival studies utilizing both hemoglobin (Cr51) and membrane (P32-phosphatidylethanolamine) labels.